mongodb/jstests/noPassthrough/aggregation_zero_batchsize.js

/**
 * Tests that a batch size of zero can be used for aggregation commands, and all data can be
 * retrieved via getMores.
 */
(function() {
"use strict";

const mongodOptions = {};
const conn = MongoRunner.runMongod(mongodOptions);
assert.neq(null, conn, "mongod failed to start with options " + tojson(mongodOptions));

const testDB = conn.getDB("test");
const coll = testDB[jsTest.name];
coll.drop();

// Test that an aggregate is successful on a non-existent collection.
assert.eq(0,
          coll.aggregate([]).toArray().length,
          "expected no results from an aggregation on an empty collection");

// Test that an aggregate is successful on a non-existent collection with a batchSize of 0, and
// that a getMore will succeed with an empty result set.
let res = assert.commandWorked(
    testDB.runCommand({aggregate: coll.getName(), pipeline: [], cursor: {batchSize: 0}}));

let cursor = new DBCommandCursor(testDB, res);
assert.eq(
    0, cursor.itcount(), "expected no results from getMore of aggregation on empty collection");

// Test that an aggregation can return *all* matching data via getMores if the initial aggregate
// used a batchSize of 0.
const nDocs = 1000;
const bulk = coll.initializeUnorderedBulkOp();
for (let i = 0; i < nDocs; i++) {
    bulk.insert({_id: i, stringField: "string"});
}
assert.commandWorked(bulk.execute());

res = assert.commandWorked(
    testDB.runCommand({aggregate: coll.getName(), pipeline: [], cursor: {batchSize: 0}}));
cursor = new DBCommandCursor(testDB, res);
assert.eq(nDocs, cursor.itcount(), "expected all results to be returned via getMores");

// Test that an error in a getMore will destroy the cursor.
function assertNumOpenCursors(nExpectedOpen) {
    let serverStatus = assert.commandWorked(testDB.adminCommand({serverStatus: 1}));
    assert.eq(nExpectedOpen,
              serverStatus.metrics.cursor.open.total,
              "expected to find " + nExpectedOpen +
                  " open cursor(s): " + tojson(serverStatus.metrics.cursor));
}

// Issue an aggregate command that will fail *at runtime*, so the error will happen in a
// getMore.
assertNumOpenCursors(0);
res = assert.commandWorked(testDB.runCommand({
    aggregate: coll.getName(),
    pipeline: [{$project: {invalidComputation: {$add: [1, "$stringField"]}}}],
    cursor: {batchSize: 0}
}));
cursor = new DBCommandCursor(testDB, res);
assertNumOpenCursors(1);

assert.throws(() => cursor.itcount(), [], "expected getMore to fail");
assertNumOpenCursors(0);

// Test that an error in a getMore using a $out stage will destroy the cursor. This test is
// intended to reproduce SERVER-26608.

// Issue an aggregate command that will fail *at runtime*, so the error will happen in a
// getMore.
res = assert.commandWorked(testDB.runCommand({
    aggregate: coll.getName(),
    pipeline: [{$out: "validated_collection"}],
    cursor: {batchSize: 0}
}));
cursor = new DBCommandCursor(testDB, res);
assertNumOpenCursors(1);

// Add a document validation rule to the $out collection so that insertion will fail.
assert.commandWorked(
    testDB.runCommand({create: "validated_collection", validator: {stringField: {$type: "int"}}}));

assert.throws(() => cursor.itcount(), [], "expected getMore to fail");
assertNumOpenCursors(0);

MongoRunner.stopMongod(conn);
}());